Polyacrylamide–hydroxyapatite composite: Preparation, characterization and adsorptive features for uranium and thorium

The composite of synthetically produced hydroxyapatite (HAP) and polyacrylamide was prepared (PAAm–HAP) and characterized by BET, FT-IR, TGA, XRD, SEM and PZC analysis. The adsorptive features of HAP and PAAm–HAP were compared for UO22+ and Th4+. The entrapment of HAP into PAAm–HAP did not change the structure of HAP. Both structures had high affinity to the studied ions. The adsorption capacity of PAAm–HAP was than that of HAP. The adsorption dependence on pH and ionic intensity provided supportive evidences for the effect of complex formation on adsorption process. The adsorption kinetics was well compatible to pseudo second order model. The values of enthalpy and entropy changes were positive. Th4+ adsorption from the leachate obtained from a regional fluorite rock confirmed the selectivity of PAAm–HAP for this ion. In consequence, PAAm–HAP should be considered amongst favorite adsorbents for especially deposition of nuclear waste containing U and Th, and radionuclide at secular equilibrium with these elements.

SEM images of hydroxyapatite (HAP) and polyacrylamide–hydroxyapatite (PAAm–HAP), and the adsorption isotherms for Uranium and Thorium.Figure optionsDownload as PowerPoint slideHighlights
► Composite of PAAm–HAP was synthesized from hydroxyapatite and polyacrylamide.
► The materials were characterized by BET, FT-IR, XRD, SEM, TGA and PZC analysis.
► HAP and PAAm–HAP had high sorption capacity and very rapid uptake for UO22+ and Th4+.
► Super porous PAAm was obtained from PAAm–HAP after its removal of HAP content.
► The composite is potential for deposition of U, Th and its associate radionuclides.